Mohegan — The Connecticut Sun were certain that WNBA MVP Elena Delle Donne would play for the Washington Mystics in Game 3 of the WNBA Finals on Sunday, no matter how bad her back was.

Ariel Atkins, another key Washington starter, was also listed as questionable due to her own back issues.

It may not have mattered if the duo hadn’t played because anyone wearing a Mystics’ blue uniform rained a 3-pointer down on the Sun. And outworked the latter on the boards.

The Mystics tied a Finals record with 16 3-pointers and downed Connecticut, 94-81, to take a 2-1 series lead in the best-of-five series before an announced sellout crowd of 9,170.

“They were just hitting tough shots,” Sun Jonquel Jones said. “A couple of times I went out on (Kristi) Toliver on a switch, and I felt like I was there in her space, and she just hit tough shots.”

Game 4 is Tuesday at Mohegan Sun Arena at 8 p.m. If the Sun win, Game 5 is Thursday at Washington, also at 8 p.m. Both games are on ESPN2.

Washington took its biggest lead, 80-62, when Toliver hit a 3-pointer from straight on with Connecticut’s Courtney Williams right in front of her.

“We know we’ve got to be better guarding the arc,” Sun Jasmine Thomas. “They put us in ball screens and got us into rotations, so we have to figure out a better way to defend them.”

The Mystics made 16 of 27 3-pointers (59.3 percent). They tied the Finals record set by the Phoenix Mercury on Sept. 8, 2007 against the Detroit Shock.

Toliver had 20 points and 10 assists for the Mystics and Emma Meesseman had 21 points and six rebounds for the Mystics.

Delle Donne, playing with a small disk herniation in her back, had 13 points and six rebounds and Natasha Cloud made a game-high five 3-pointers for 19 points.

“We really didn't know if I was going to be able to go today because I hadn't done anything until right up before the game,” Delle Donne said. “We were able to kind of test it a little bit and go from there.”

Alyssa Thomas had 13 points, nine assists and eight rebounds, Jasmine Thomas had 16 points and six assists, and Shekinna Stricklen scored 16. Reserve Bria Holmes added 15 points.

A slow start also hurt Connecticut as it fell behind, 32-17, after the first quarter.

It was the same kind of bad start the Sun had in their 95-86 loss in Game 1 on Sept. 29. The Mystics shot 72.2 percent in that first quarter and led, 30-17.

“We talked briefly at the end of (Sunday's) game (about that),” Connecticut head coach Curt Miller said. “All three games have been decided in the first quarter, essentially. There hasn't been a close first quarter in this series yet. So we were always playing catch up. ... We expended a lot of energy.”

What was perhaps more troubling for the Sun was that the Mystics beat them on the boards, 34-27, one of their biggest strengths.

Connecticut outrebounded Washington, 41-27, in last Tuesday’s 99-87 win in Game 2. That included a crazy 17-6 edge in offensive rebounds. It also helped them to a 28-10 advantage in second-chance points.

Connecticut and the Mystics both had seven offensive rebounds Sunday, but the latter had more second-chance points (13-9).

Asked if the Mystics were more aggressive than they were on the boards, Jasmine Thomas said, “They absolutely did a better job at that. And that’s on us. That’s just a toughness thing, wanting to be physical. Wanting to own the board. That’s not always on the post players. That’s on the guards, too.”

• Jones earned her second All-WNBA second-team honor as the league announced its first and second teams on Sunday. Jones averaged a team-high 14.6 points, a league-high 9.7 rebounds, and tied for the league lead in blocks per game (2.0). She was also an All-Defensive Team first-team pick for the first time.

n.griffen@theday.com